foo.cpp: In function 'int main()':
foo.cpp:52:23: error: 'log' was not declared in this scope
  cout << floor(n*log(2)/log(10)) + 1 << endl;
                       ^
foo.cpp:52:32: error: 'floor' was not declared in this scope
  cout << floor(n*log(2)/log(10)) + 1 << endl;
                                ^